Borate substituted ettringites
Conference
·
OSTI ID:62210
- Univ. of Aberdeen, Old Aberdeen, Scotland (United Kingdom)
The setting of cement is adversely affected by soluble borates. To reduce interference, the extent to which borate can be insolubilized has been investigated. One specific mechanism of insolubilization is by inclusion into ettringite. Ettringite, Ca{sub 6}Al{sub 2}(SO{sub 4}){sub 3}(OH){sub 12}{center_dot}26H{sub 2}O, is a normal and stable constituent of Portland cement. It has an open but non-zeolitic framework. Borate can substitute partially or fully for sulfate. Formation conditions, solubility and stability of borate ettringites, Ca{sub 6}Al{sub 2}(BO{sub 4}){sub 2-4}(OH,O){sub 12}{center_dot}26H{sub 2}O, are characterized using XRD, IR, DTA, and SEM. The potential durability of borate ettringites in a repository environment have been assessed by exposing it to Na-sulfate and Na-carbonate attack at different concentrations. Ion exchange occurs; back substitution of borate by sulfate is incomplete; high carbonate concentrations can, however, decompose borate ettringite. On heat treatment up to 85{degrees}C the crystalline morphology and the OH arrangement of the structure are altered, but the X-ray powder pattern, and hence its structural framework are largely unaffected. It is concluded that ettringite has potential to reduce the solubility of borate.
- OSTI ID:
- 62210
- Report Number(s):
- CONF-921101--Vol.294
- Country of Publication:
- United States
- Language:
- English
Similar Records
Preferred orientation of ettringite in concrete fractures
Vibrational spectroscopy of functional group chemistry and arsenate coordination in ettringite
Investigation of the structure of ettringite by time-of-flight neutron powder diffraction techniques
Journal Article
·
Fri Jan 30 23:00:00 EST 2009
· Journal of Applied Crystallography
·
OSTI ID:960280
Vibrational spectroscopy of functional group chemistry and arsenate coordination in ettringite
Journal Article
·
Sat Oct 31 23:00:00 EST 1998
· Geochimica et Cosmochimica Acta
·
OSTI ID:338619
Investigation of the structure of ettringite by time-of-flight neutron powder diffraction techniques
Journal Article
·
Tue Feb 14 23:00:00 EST 2006
· Cement and Concrete Research
·
OSTI ID:20793275